1. Field of the Invention
The present invention relates to a method for manufacturing a lens cap, and particularly to a method for manufacturing a lens cap for an optical module such as a transceiver, an optical sub assembly, or a semiconductor laser device.
2. Related Art
The field of optical communication is developing rapidly, and optical modules having greater performance are being designed to satisfy new system needs. Since optical modules, such as laser devices, are easily affected by their environments, the major optical elements of an optical module are generally sealed in a structure such as a lens cap.
A conventional laser device is disclosed in Japanese Patent Publication No. 63-84184 (see FIG. 5). The laser device 10 includes a base 11 and a lens cap 18. The lens cap 18 includes a housing 16 and a glass plate 17. A laser diode 14 and an optical detector 15 are received in an enclosure formed by engagement of the housing 16 to the base 11. The housing 16 includes an inclined plane 12 on a top thereof, which defines an opening 13 therein for transmission of a beam of light. The glass plate 17 is attached to the housing using adhesive to cover the opening 13, and functions to transmit and reflect beams of light and to seal the enclosure. A beam of light emitted by the laser diode 14 is divided into two portions by the glass plate 17, one portion being transmitted through the opening 13 via the glass plate 17, and the other portion being reflected into the optical detector 15 by the glass plate 17, and thereby being detected.
However, since the glass plate 17 is attached to the housing 16 by adhesive, and adhesive is easily smeared, the glass plate can be contaminated by smeared adhesive and the transmittance of the glass plate can therefore be affected. Moreover, some adhesives are susceptible to losing strength under mechanical impact or in high temperature environments, which can reduce performance of the device. Furthermore, using adhesive complicates the manufacture and makes the device more expensive.
Accordingly, an improved lens cap for an optical module and a method for making the same are desired to overcome the above problems.